This invention relates to torque wrenches. More particularly, this invention relates to gear driven torque wrenches which have an input connected through a gear system to an output and a reaction member for grounding the wrench during operation. Such wrenches are typically manually operated by means of a crank or the like at the input, and such wrenches may be referred to herein as manually operated wrenches. It will, however, be understood that such wrenches may also be operated by means of power assist at the input, such as air or electrically driven inputs, and any such power assisted input is also within the scope of the invention of this application.
A well known and typical manually operated power wrench of the prior art is shown in U.S. Pat. No. 3,683,686 to Sergan which is assigned to Raymond Engineering Inc.,the assignee hereof. That wrench is commercially available from Raymond Engineering Inc. as the mold PD 1201 wrench. In the normal operation of the Raymond PD 1201 wrench, the wrench is grounded for reaction by the grounding pins (24, 26) at the bottom of the wrench, and the input is by means of a crank or other drive mechanism to the input socket (44). With the wrench of the Sergan patent, and other mechanical torque wrenches of that general type, the rotation of the output socket (40) of the wrench (i.e., the direction of rotation of the output) is in the same direction as the input. However, some situations are encountered where, because of the arrangement and location of parts to be torqued, it is necessary to ground the wrench for reaction at the output socket and torque the part to be torqued by rotation of the body of the wrench. Connection between the wrench body and the part to be torqued is then effected by means of an adapter connected to what would normally be the reaction pins; and an adapter is typically required to connect the output socket to a grounded location for reaction. This mode of operation will be referred to herein as a reverse mode of operation.
A particularly troublesome problem when the wrench is operated in the reverse mode described above (i.e., when grounding is through the normal output socket and torquing is accomplished via the normal reaction pins) is that the output of the wrench is in the reverse direction of the input. In normal operation of the wrench, a clockwise input (typical for tightening) will result in a clockwise output, and the operator has the comfortable feeling that he has a direct and natural connection to the part being torqued. However, when the wrench is operated in the reverse mode, the input and output directions are reverse to each other. That is, a clockwise input (normal for tightening) will result in a counterwise rotation of the wrench case (i.e., a reaction opposite to the grounding load). Therefore, when the wrench is operated in the reverse mode, the operator must input in the counterclockwise mode (i.e., opposite to normal operation) to effect torquing operation to tighten an element. This requirement to input in the direction reverse to the normal input produces operator confusion and error and has resulted in broken adapters and stripped threads. There is, therefore, a need for a dual mode wrench where the input and output are in the same direction regardless of the mode of operation.